The add-on effect of a Chinese herbal formula for patients with resistant hypertension: study protocol for a pilot cohort study.

BACKGROUND Despite a recent American Heart Association (AHA) consensus statement emphasizing the importance of resistant hypertension (RH), its control is still a challenge for conventional medicine. The Chinese herbal formula, Qutan Huayu Fang, has been used effectively to assist antihypertensive agents in blood pressure control, but its effect for RH patients is still unclear. This pilot study aims to explore the effects of taking the formula in addition to antihypertensive medication in the management of RH. METHODS/DESIGN A prospective cohort study will be conducted in two first-class hospitals of traditional Chinese medicine (TCM). Eligible RH patients will be classified as the experimental group (n = 100) and the control group (n = 100) based on the interventions they receive. Participants taking antihypertensive agents and the Chinese herbal formula will be in the experimental group and those taking antihypertensive agents alone will be in the control group. The whole study will last 24 weeks, including an 8-week observation and follow-up at 24 weeks. The primary outcomes, assessed against patient baseline conditions, will be the reduction of systolic blood pressure and diastolic blood pressure as well as changes in TCM symptoms and signs. These outcomes will be assessed at weeks 2, 4, 6, and 8. The reductions of blood pressure will also be assessed at week 24. Cardiac events and mortality rate will be secondary outcomes and will be assessed at weeks 8 and 24. Any adverse reactions will be recorded during the study. The causal inference method will be used to assess the effectiveness of the inclusion of TCM herbal medicine in the management of patients with RH. DISCUSSION This study will determine whether the Chinese herbal formula is helpful for RH patients treated with antihypertensive agents and the findings will provide a basis for further confirmatory studies.